在R数据框中如何按年份和月排序? [英] How to sort by year AND month in R data frame?
问题描述
我正在尝试订购一系列我已经存储在数据框中的时间数据。格式为:
I am trying to order a series of time data I have stored in a data frame. The format is of:
"%Y-%b"
其中看起来像2009-Sep
等。
到目前为止,我已经设法找到这种方法:
Until now I have managed to find this method:
ds[order(as.Date(ds$yearmonth, format="%Y-%b")),]
但是它只按年份排序,然后按照字母顺序排列月份,给我一个订单 2009-Jan
, 2009 -Jul
, 2009-Jun
等我很困惑,这不是一个容易解决的问题。
But it only sort by year, and then it moves to alphabetical order regarding the months, giving me an order of 2009-Jan
, 2009-Jul
, 2009-Jun
etc. I am quite puzzled this is not an easy problem to fix.
请帮助...
最佳
Kasper
Best Kasper
推荐答案
包中的 as.yearmon()
函数(和yearmon
类) 动物园是为这种数据设计的:
The as.yearmon()
function (and the "yearmon"
class) in package zoo is designed for this sort of data:
dat <- c("2009-Sep","2009-Feb","2009-Jan")
require(zoo)
d2 <- as.yearmon(dat, "%Y-%b")
> sort(d2)
[1] "Jan 2009" "Feb 2009" "Sep 2009"
> order(d2)
[1] 3 2 1
> d2[order(d2)]
[1] "Jan 2009" "Feb 2009" "Sep 2009"
您可以在每个日期的某一天($ code)paste0(),并胁迫到Date
通过 as.Date()
但 as.yearmon()
对我来说似乎更自然:
You could of course paste0()
a day onto each date and coerce to class "Date"
via as.Date()
but as.yearmon()
seems more natural to me:
> as.Date(paste0(dat, "-01"), "%Y-%b-%d")
[1] "2009-09-01" "2009-02-01" "2009-01-01"
注意,您可以通过强制yearmon生成相同的结果
对象到as.Date
,例如:
Note you can generate that same result by coercing the "yearmon"
object to class "as.Date"
, e.g.:
> as.Date(d2)
[1] "2009-09-01" "2009-02-01" "2009-01-01"
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